Digital data transmission is often accomplished using modulation schemes. For higher data rates, the equalizer complexity involved for single carrier modulation grows with the symbol rate and as a result multicarrier transmission schemes such as orthogonal frequency-division multiplexing (OFDM) typically are utilized instead. Many higher data rate systems such as systems compliant with a Wireless Fidelity (Wi-Fi) Alliance standard, a Worldwide Interoperability for Microwave Access (WiMAX) standard, a Digital Video Broadcasting-Terrestrial (DVB-T) standard, a Long Term Evolution (LTE) standard, and so on, use multicarrier modulation for this reason. Many of these systems are utilized in environments with heavy multipath propagation and/or dynamic fading, often wherein one or both of the link terminals are non-stationary. Even when the link terminals are stationary, dynamic changes in the environment, for example trucks passing by on nearby streets, may create rapid changes in the channel that challenge the synchronization capabilities of the demodulator.
Recent advances in video compression technology have greatly reduced the data rates involved to transport video data streams. Such advances have provided an opportunity to reduce the signal bandwidth used to transport video data. A reduction in signal bandwidth via compression allows certain benefits such as power concentration to increase link margin. Compression has also reopened the door for the use of single carrier modulation schemes since the equalizer complexity is more manageable at the reduced signal bandwidths. However, single carrier signal synchronization, especially carrier phase tracking, can be very difficult in fading conditions at the involved signal bandwidths which are narrower than the bandwidths for typical broadband systems, for example WiFi at 20 MHz or DVB-T at 8 MHz, and broader than the bandwidths for most cellular systems, for example 500 kHz to 1 MHz. At these intermediate signal bandwidths, both the narrow signal techniques used for many cellular systems and the broadband techniques used for higher-rate signals may be suboptimal.
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